Jane Austen is a phenomenon, but it’s a little hard to say exactly what kind. For about a century and a half, Miss Austen or “dear Jane” flew under the radar of scholarship, but now scholars of every fashionable school, in their business-like way, deal with Austen. Almost all authors, when they move up (down? over?) into course reading lists, stop being read for fun. Jane Austen’s six novels, though, still reside on the night tables of people who aren’t paying or being paid to read them.

And Austen readers can read – well, I won’t quite say obsessively, but with a ferocious personal passion unmatched even by Jane Eyre. As David Lodge’s professor Morris Zapp gripes, “Even the dumbest critic understood that Hamlet wasn’t about how the guy could kill his uncle, or the Ancient Mariner about cruelty to animals, but it was surprising how many people thought that Jane Austen’s novels were about finding Mr. Right.”

You have to be very highly educated indeed to think that Jane Austen’s novels aren’t about finding Mr. Right, at least in part. It is, after all, prudent to learn how to identify the Mr. Collinses, Mr. Eltons, Mr. Wickhams, and Willoughbys one meets before one marries them. Still, it is true that Austen fans can sometimes step over a line separating fiction from life.

There is a very long bibliography of sequels to Austen novels by diverse hands. Take “Mr Darcy Takes a Wife” – please. This is a perfervid piece of fan fiction depicting the sexual married life of Lizzie Bennet and Fitzwilliam Darcy, complete with bloodstained sheets on the wedding night. Then there’s the online fan-fiction. One example that caught my eye details the adventures of Elizabeth and Darcy on the Starship Enterprise.

Halfway between the viscous vigor of the fans and the dry distance of the academics is the English literary scholar Richard Jenkyns’s recent book. In “A Fine Brush on Ivory: An Appreciation Of Jane Austen” (Oxford University Press, 215 pages, $25), attractively short, he pleasantly admits to having no overriding thesis and no plans to be comprehensive.

Mr. Jenkyns’s title comes from an only apparently self-deprecatory description Austen gave of her writing to a nephew: “the little bit (two Inches wide) of Ivory on which I work with so fine a Brush, as produces little effect after much labour.” Mr. Jenkyns’s ear hears irony here. To his mind, Austen is, quite simply, a genius.

And he doesn’t think it very hard to prove: “Virginia Woolf once said about Jane Austen that ‘of all great writers she is the most difficult to catch in the act of greatness.’ It is quite false: there is hardly another novelist of whom one may so readily say, “That chapter, that paragraph, that sentence is a moment of genius.”

Mr. Jenkyns partly aims to whip the curtain off those moments of Austen’s “bravura technique” where “We should realize that she is exulting in the sheer ingenuity of her performance, and an enjoyment of that virtuosity is a proper part of our own aesthetic pleasure.” This is indeed a book filled with pleasures.

Since Austen’s few minor characters are among the greatest joys of reading her fiction, I particularly enjoyed Mr. Jenkyns’s corrective thoughts on E.M Forster, who first deployed the notions of flat and round characters. Who at first could seem flatter than Lady Bertram, who spends almost the whole of “Mansfield Park” literally prone on a sofa? But her flatness does not, according to Mr. Jenkyns, point to any deficiency of imagination or observation on Austen’s part; quite the contrary.

She is not so much a flat character as a flattened character – her dull, pampered life has drained from her the possibility of variety of response. … The flatness is a truth about her nature rather than a description of the novelist’s technique. Like the animal in the cartoon, she has been squashed flat.

Austen’s technique is in the service of her “moral genius.” Once again important revelations come out of the minor characters. Thus Mr. Woodhouse is, at one and the same time, “a lovable old silly” and “a monster, the villain of the piece.” And Mr. Jenkyns is very attentive to the details Austen provides about horrid Aunt Norris, pent in a Sartrean hell in the “brutal” closing lines of “Mansfield Park,” that odd novel: ” ‘Mansfield Park’ is Jane Austen’s problem novel, and as with ‘Don Giovanni’ and ‘Measure for Measure’ we may perhaps reckon it to be a comedy, but only just.”

Mr. Jenkyns’s Austen is perfectly aware that among the “few country families” she paints on that “little bit of ivory” can reside real cruelty and even evil. But she is also acute enough to see the less obvious moments of heroism and grace. When Darcy, early in “Pride and Prejudice,” observes a bit censoriously, “In a country neighbourhood you move in a very confined and unvarying society,” Mr. Jenkyns has this to say: “Criticizing Jane Austen is among those faults of which Darcy needs to be cured.”